1. Field of the Invention
The present invention relates generally to riding-type concrete finishing machines. More particularly, the present invention relates to riding-type concrete finishing trowels comprising a pair of rotatable blade-equipped rotors including control means for independently tilting the levers to effectuate enhanced steering. Representative self propelled riding trowels are classified in U.S. Class 404, Subclass 112.
2. Description of the Prior Art
As will be recognized by those skilled in the art, it has long been well known that wet concrete must be appropriately finished. A wide variety of manually pushed troweling machines have previously been proposed. However, self propelled riding trowels finish the concrete quicker and more efficiently. Riding trowels enable a user to be seated upon the trowel frame, and the revolving rotors beneath the frame directly contact the surface of the concrete.
Machines of this general nature include some form of frame from which two or more rotating blades downwardly project. The blades are propelled by a self contained motor mounted on the frame, which may be linked to rotor gear boxes. The blades are controlled by gear mechanisms having a rotatable axis generally perpendicular to the frame, and a yoke controlled bearing assembly is often employed to vary rotor pitch. The weight of the trowel and the operator is transmitted frictionally to the concrete by the revolving blades. Steering is accomplished by tilting the blade rotor assemblies to generate differential vector forces which propel the frame.
Two of the most relevant prior art riding trowels known to us are seen in U.S. Pat. Nos. 3,936,212, Issued Feb. 3, 1976 and 4,046,484, Issued Sep. 6, 1977. Both of the latter machines employ a frame having a seat for the operator which mounts two or more bladed rotors which project vertically downwardly underneath the frame carriage. Blades twistably associated with each rotor directly contact the concrete surface. Tilting forces on the rotors effectuate steering of the machine in various directions. The blades are rotated relative to the rotors (i.e. twisted) to effectuate different finishing characteristics by changing blade pitch. Both of the latter patents disclose lever means projecting vertically upward from the frame which may be manipulated by the driver to effectuate blade control. In U.S. Pat. No. 3,936,212, three individual rotor assemblies are shown, and none of the blades interlap with one another. In U.S. Pat. No. 4,046,484, the trowels intermesh to work overlapping circles, providing a gapless characteristic to obtain maximum width of surface coverage. More importantly, U.S. Pat. No. 4,046,484 teaches that rotor tilting forces needed for steering control may be applied to one of the rotors in two planes, whereas only a single plane of tilting is required for the other rotor.
A basic version of a twin rotor riding machine for surface finishing of concrete is seen in U.S. Pat. No. 2,898,826, Issued Aug. 11, 1959. U.S. Pat. No. 4,859,114, Issued Aug. 22, 1989 discloses a system for providing steering in a twin rotor concrete trowel by varying the position of frame sections to effectuate relative tilting movements of various frame portions. U.S. Pat. No. 4,784,519, Issued Nov. 15, 1988, discloses a linkage system for varying the pitch of the blade systems in unison, and an interlink system for tilting each blade to effectuate directional control. Other related riding trowels are seen in U.S. Pat. Nos. 4,775,306; 2,869,442; and 4,710,055.
However, as will be recognized by those skilled in the art, steering of all known riding trowels is cumbersome and difficult. Steering responses lag the lever inputs necessary to transmit and generate steering control instructions. It is often difficult for the contractor or owner of the machine to train an operator to properly use riding trowels in a short period of time. Even where the operator is relatively familiar with riding trowels, current steering systems are very challenging, and the steering response of known machines invites errors, collisions and accidents. Moreover, because of the typical blade and rotor assembly linkage construction employed in the prior art, impacting vibrations experienced on one rotor deleteriously affect movements of the other. The latter "bump-steering" problem compounds conventional riding trowel control deficiencies. When operating finishing machines with conventional blade-controlling linkages in tightly confined areas where various obstacles exist, operation of conventional machines is slow and clumsy.
Prior art machines are also difficult to set up. Usually blade pitch control is difficult to set, and it has been difficult in the past for operators to measure pitch. Another problem is that it is sometimes difficult for an operator to clearly see those areas of the concrete surface which may need finishing the most. No known machines provide a means for sensing irregular surface areas.
Hence it is important to provide a self propelled motorized riding trowel which is capable of succinct and delicate maneuvers and which is relatively easily controlled by the operator. It is also important to provide a highly maneuverable self propelled riding trowel of the character described which can be mastered by a operator in a short period of time, and which steers in a responsive, predictable manner.